1 #include <linux/module.h>
2 #include <linux/glob.h>
3
4 /*
5 * The only reason this code can be compiled as a module is because the
6 * ATA code that depends on it can be as well. In practice, they're
7 * both usually compiled in and the module overhead goes away.
8 */
9 MODULE_DESCRIPTION("glob(7) matching");
10 MODULE_LICENSE("Dual MIT/GPL");
11
12 /**
13 * glob_match - Shell-style pattern matching, like !fnmatch(pat, str, 0)
14 * @pat: Shell-style pattern to match, e.g. "*.[ch]".
15 * @str: String to match. The pattern must match the entire string.
16 *
17 * Perform shell-style glob matching, returning true (1) if the match
18 * succeeds, or false (0) if it fails. Equivalent to !fnmatch(@pat, @str, 0).
19 *
20 * Pattern metacharacters are ?, *, [ and \.
21 * (And, inside character classes, !, - and ].)
22 *
23 * This is small and simple implementation intended for device blacklists
24 * where a string is matched against a number of patterns. Thus, it
25 * does not preprocess the patterns. It is non-recursive, and run-time
26 * is at most quadratic: strlen(@str)*strlen(@pat).
27 *
28 * An example of the worst case is glob_match("*aaaaa", "aaaaaaaaaa");
29 * it takes 6 passes over the pattern before matching the string.
30 *
31 * Like !fnmatch(@pat, @str, 0) and unlike the shell, this does NOT
32 * treat / or leading . specially; it isn't actually used for pathnames.
33 *
34 * Note that according to glob(7) (and unlike bash), character classes
35 * are complemented by a leading !; this does not support the regex-style
36 * [^a-z] syntax.
37 *
38 * An opening bracket without a matching close is matched literally.
39 */
glob_match(char const * pat,char const * str)40 bool __pure glob_match(char const *pat, char const *str)
41 {
42 /*
43 * Backtrack to previous * on mismatch and retry starting one
44 * character later in the string. Because * matches all characters
45 * (no exception for /), it can be easily proved that there's
46 * never a need to backtrack multiple levels.
47 */
48 char const *back_pat = NULL, *back_str;
49
50 /*
51 * Loop over each token (character or class) in pat, matching
52 * it against the remaining unmatched tail of str. Return false
53 * on mismatch, or true after matching the trailing nul bytes.
54 */
55 for (;;) {
56 unsigned char c = *str++;
57 unsigned char d = *pat++;
58
59 switch (d) {
60 case '?': /* Wildcard: anything but nul */
61 if (c == '\0')
62 return false;
63 break;
64 case '*': /* Any-length wildcard */
65 if (*pat == '\0') /* Optimize trailing * case */
66 return true;
67 back_pat = pat;
68 back_str = --str; /* Allow zero-length match */
69 break;
70 case '[': { /* Character class */
71 if (c == '\0') /* No possible match */
72 return false;
73 bool match = false, inverted = (*pat == '!');
74 char const *class = pat + inverted;
75 unsigned char a = *class++;
76
77 /*
78 * Iterate over each span in the character class.
79 * A span is either a single character a, or a
80 * range a-b. The first span may begin with ']'.
81 */
82 do {
83 unsigned char b = a;
84
85 if (a == '\0') /* Malformed */
86 goto literal;
87
88 if (class[0] == '-' && class[1] != ']') {
89 b = class[1];
90
91 if (b == '\0')
92 goto literal;
93
94 class += 2;
95 /* Any special action if a > b? */
96 }
97 match |= (a <= c && c <= b);
98 } while ((a = *class++) != ']');
99
100 if (match == inverted)
101 goto backtrack;
102 pat = class;
103 }
104 break;
105 case '\\':
106 d = *pat++;
107 fallthrough;
108 default: /* Literal character */
109 literal:
110 if (c == d) {
111 if (d == '\0')
112 return true;
113 break;
114 }
115 backtrack:
116 if (c == '\0' || !back_pat)
117 return false; /* No point continuing */
118 /* Try again from last *, one character later in str. */
119 pat = back_pat;
120 str = ++back_str;
121 break;
122 }
123 }
124 }
125 EXPORT_SYMBOL(glob_match);
126